Adaptations to Arid Habitats
What is an arid habitat? Arid habitats: are extremely dry receive little or no rainfall usually have high temperatures may suffer periodic droughts
Where are arid habitats found? Estimates suggest that arid and semi arid habitats account for more than one third of the earthâ€™s land surface
Credit: U. S. Geological Survey
What are the challenges of living in an arid habitat? Lack of plants
Lack of water Challenges?
Lack of food
Temperature Movement Cold
What is adaptation? “the process whereby a species evolves characteristics that enable it to survive in a particular habitat” Adaptations allow species to live successfully in their habitat Species living in different habitats need different adaptations Adaptations can be behavioural or physical
Barrow Island: Case Study - Approximately 70 km off the coast of Western Australia - Receives an average of 320 mm rainfall per year - Most of the island is covered by spinifex grassland - Nearly 2,600 different species have been recorded here
A flooded channel on the west coast of the island, a rare and important source of freshwater on Barrow
Mammals on Barrow Island Common wallaroo (Macropus robustus) Found across most of Australia, with one subspecies on Barrow Island Seeks shelter in caves and rocky outcrops Can go for a few months without drinking Licks saliva onto forearms to help it lose heat through evaporation Stops breeding during prolonged droughts, but breeds quickly in good conditions
Other mammal examples Wild Bactrian camel Many adaptations to conserve water, cope in intense heat and survive sandstorms!
Bat-eared fox Large ears to help dissipate heat
Fawn hopping mouse Can obtain water from seeds Produces concentrated urine + dry faeces Shelters in a burrow during day
Kangaroo rats â€˜Nasal counterflow systemâ€™ reduces water lost through breathing
Amphibians on Barrow Island Mainâ€™s frog (Litoria maini) Only amphibian species found on Barrow Island Spends the dry season underground in a state of torpor Produces a membrane over the skin to prevent drying out Only emerges after rainfall Eggs laid in temporary pools, tadpoles develop quickly
Other amphibian examples Spotted marsh frog Shelters under logs and stones in the heat of the day
Water holding frog Can reabsorb water stored in its bladder or pockets under the skin
Green tree frog Takes refuge in any available water sources, including pipes, water tanks and toilet bowls!
Reptiles on Barrow Island Perentie (Varanus giganteus) General adaptations common to reptiles Shelters underground or in rock shelters; basks in sun in early morning and late afternoon On very hot days, may shelter in shade or climb termite mounds or shrubs to get off hot ground
Other reptile examples Thorny devil Tiny grooves over body direct moisture to the mouth Can change colour depending on temperature
Desert tortoise Dormant during hottest part of summer (aestivation) Lives in burrows
Eastern sandfish Streamlined body allows it to ‘swim’ through sand
Saudi fringe-fingered lizard Fringes of elongated scales on the toes help in moving across sand
Sidewinder ‘Sidewinding’ movement across loose sand
Plants on Barrow Island Spinifex grass (Triodia species) Extensive root system to collect water both from the surface and underground. Roots can be up to 3 metres long. Leaves have a waxy, impermeable surface (cuticle) to reduce water loss. Leaves curl inwards into long pointed tubes to slow the rate of transpiration.
Other plant examples
Lava cactus Stores water in thick stems, leaves reduced to spines to reduce transpiration
Grandidierâ€™s baobab Stores water in trunk which can expand after rainfall
Bristlecone pine Parts of the living tissue die back during drought. Can still produce cones and seeds when conditions improve
Activity 1 You will be given a worksheet with a list of adaptations species use to survive in arid habitats. Your task is to decide whether each adaptation is a behavioural or a physical adaptation.
Activity 1 - Answers Adaptation
Producing concentrated urine
Ability to withstand high body temperatures Seeking shade
Ability to store water inside the body
Living in a burrow
Large surface area
Leaves reduced to spine
Breed only after rainfall Nasal counterflow
Summary • Arid habitats are dry areas with little rainfall and are usually hot, although they can be cold at night. • Arid habitats cover over a third of the Earth’s land surface. • Animals and plants have evolved a range of adaptations to help them survive in arid habitats. • These adaptations can be behavioural, such as sheltering in a burrow during the heat of the day, or physical, such as having a large surface area to lose heat more quickly.
Activity 2 The aim of this activity is to compare how effective different adaptations are at helping a species to conserve water. You will be given sponges soaked in water to represent your arid â€œanimalsâ€?. You need to design an experiment to measure how much water your sponges lose under various conditions set up to represent different adaptations. You need to weigh the sponges before and after the experiment so that you can record how much weight (water) each has lost.